This invention relates generally to fire doors having windows and, more particularly, to a means for securing and framing or trimming a pane of glass that serves as a light or vision panel in a fire retardant door. Such doors usually comprise a core of incombustible mineral material and certain of the doors are provided with an overlay on each surface in the form of a wood veneer Which is bonded to the door surface. The doors are installed in buildings to prevent the spread of fire from one part of the building to another and to fulfill this purpose the doors must of course be substantially incombustible. Nevertheless fire doors, as part of the interior of a living space, must have at least minimal aesthetic characteristics. Accordingly, the wood veneer is provided as on the aforesaid surfaces of the doors and in certain fire doors, the framing or trimming of the window or vision panel is also provided with a wood veneer. The glass pane is conventionally of the imbedded wire mesh type.
From the foregoing it will be apparent that the glass pane must be sealed around its edge to the incombustible core of the fire door and a thermal barrier must be provided by the frame and/or the trim of the window. Thus, the window frame or trim must satisfy both functional and aesthetic characteristics.
Metal frames have been used for fire door windows and have been painted to match or simulate wood but are not wholly satisfactory from an aesthetic standpoint. U.S. Pat. No. 4,637,182 to Ellsworth et al entitled Windowed Fire Door discloses a framing or trimming system wherein "bead strips" of an incombustible mineral material are provided with a wood veneer bonded thereto. The window pane is held in position by a plurality of small clips and associated nails which extend into the incombustible core of the fire door. While this construction is generally satisfactory, difficulties are encountered in installation with the plurality of small metal clips and it will of course be apparent that retention of the window pane by the clips is non-uniform along the edge of the pane. Further, adhesive bonding of the wood veneer to the mineral material of the incombustible bead strips may be less than satisfactory over time.
It is the general object of the present invention to provide an improved window trim construction wherein both thermal barrier and aesthetic requirements are fully met, wherein the retention of the pane of glass is both secure and uniform along the edge of the pane of glass, and wherein bonding of the wood veneer to the underlying material is secure over long service life.